JP2000214786A - Plane display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a distortion due to thermal extension/contraction of an optical system sheets placed on a surface light source and an image display defect due to that by holding an optical sheet in shiftably in position between a display panel and the light source and fixing it in one side area of four sides surrounding an image display area. SOLUTION: An optical overlapped sheet 1 constituted so that three sheets of optical sheets 11-13 are overlapped is arranged between the upper surface of the surface light source 3, that is, a light-emitting surface and the lower surface of the display panel 2. This optical overlapped sheet 1 is prolonged between a lamp reflector 33 and the display panel 2 in the side that a tubular light source 32 is arranged. That is, the optical overlapped sheet 1 is sandwiched between the lamp reflector 33 and the display panel 2 to be fixed in the area along the tubular light source 32 in a frame area. This optical overlapped sheet 1 is fixed only in this area, and isn't fixed in the emission area of the light source light and on the other three sides sides.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat panel display device having a surface light source device on the back side of a display panel.

[0002]

2. Description of the Related Art A flat display device such as a liquid crystal display device has been used as an image display device for a television, various computers, a car navigation system, etc. by taking advantage of features such as thinness, light weight, and low power consumption. Have been.

For example, a light transmission type liquid crystal display device includes a liquid crystal panel having a liquid crystal layer held between a pair of transparent substrates,
A surface light source device disposed on the back surface of the liquid crystal panel (the surface opposite to the image display surface) to guide light source light to the liquid crystal panel; Hereinafter, the back side will be described below.

In order to reduce the thickness and size of such a flat display device, it is necessary to reduce the thickness of the surface light source device. Therefore, surface light source device (backlight)
The edge light method has become the mainstream.

An edge light type surface light source device is disclosed in, for example, Japanese Utility Model Laid-Open Publication No. 63-24529, which discloses a tubular light source and a thin plate made of an acrylic resin or the like having a milky white scattering pattern printed on the back side. Including a light guide plate of a shape,
One end face of the light guide plate is arranged close to the tubular light source. And the light source light from the tubular light source propagates through the light guide plate and is scattered by the scattering pattern on the back surface of the light guide plate,
Light is emitted from the main surface of the light guide plate on the liquid crystal panel side.

[0006] Between the surface light source device and the display panel, optical sheets such as a prism sheet and a diffusion sheet are arranged so as to overlap each other. The diffusion sheet is to make the luminance emitted from the light guide plate upward in the emission surface more uniform. The prism sheet improves the front luminance by converging the emitted light in the front direction.

In this specification, a sheet including a film having a considerably small thickness is referred to as a sheet.

A conventional flat panel display device is a notebook PC.
An example of a backlight-type liquid crystal display device used for the above-described method will be described with reference to FIG.

The flat panel display device 100 includes a rectangular display panel 102, a frame-shaped metal bezel cover 104 and a plastic frame 105 sandwiching the four peripheral edges of the display panel 102 from above and below, and a lower part of the display panel 102. , A light guide plate 131 arranged along at least one side end face of the light guide plate 131, and a driving printed board arranged on the lower surface of the light guide plate 131 106
Consists of Further, the tubular light source 132 is covered with a lamp mirror 135 made of an aluminum foil laminated film or the like for collecting light from the light source to the light guide plate. The tubular light source 132 is further covered with an L-shaped lamp cover 107 from below.

Here, the display panel 102 and the light guide plate 131 are used.
The optical system overlap sheet 101 in which three optical system sheets are overlapped is disposed in the gap between.

Generally, this optical system stack sheet 101 is
It is placed on the light guide plate 131 so as to be slightly displaced,
Sufficient play was provided between the optical system overlapping sheet 101 and its four frames.

Since the optical system laminated sheet 101 usually has a larger coefficient of thermal expansion than the light guide plate 131, the expansion of the optical system laminated sheet 101 due to heat is absorbed by this play.

[0013]

However, as the demand for reducing the ratio of the image non-display area (frame area) of four circumferences in the flat display device (narrowing of the frame area) becomes stricter year by year, the optical system overlapping sheet 101 is required. It has become increasingly difficult to have enough play between the game and the frames. For this reason, when the optical system laminated sheet 101 greatly expands, it cannot spread outward, and "undulation" occurs near the edge.

Also, the optical system overlapping sheet 101 may receive more heat from the tubular light source in a portion close to the tubular light source and locally cause thermal expansion. Even when a good play can be taken, uneven brightness due to local distortion of the optical overlap sheet 101 may occur.

FIG. 4 schematically shows a case in which four rounds of play are not sufficiently provided and local heating is applied near the tubular light source. As schematically shown in the figure, the swell at the edge where the tubular light source is arranged is other than the uneven brightness,
This causes light leakage and causes display defects such as bright spots.

These display defects caused by the distortion of the optical system overlapping sheet 101 are caused by the demand for display performance as the definition of an image in a flat display device is enhanced and the display performance is increased.
It has been a problem.

If the optical system stack sheet 101 is firmly attached to the upper surface of the light guide plate 131, the work load and the manufacturing cost increase.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in a flat panel display device having a surface light source and optical sheets, distortion due to thermal expansion and contraction of optical sheets mounted on the surface light source. And a flat-panel display device capable of suppressing image display defects caused by this.

[0019]

According to a first aspect of the present invention, there is provided a flat panel display device comprising: a light transmission type display panel in which a plurality of pixels are arranged in an image display area; and a display panel arranged behind the display panel. A flat panel display device comprising: a surface light source that emits light from a light source; and an optical system sheet disposed in a gap between the display panel and the surface light source in a region including at least the image display region; In the frame area surrounding the four circumferences, in at least one side of the four circumferences, the optical system sheet is sandwiched and fixed between the display panel and the surface light source so as not to be displaced. I do.

With such a configuration, distortion due to thermal expansion of the optical system sheet and luminance unevenness caused by the distortion can be significantly suppressed.

According to a second aspect of the present invention, in the flat display device, the surface light source includes a substantially rectangular light guide plate, and a tubular light source disposed on at least one side of the substantially rectangular shape and close to a side end surface of the light guide plate. And the optical system sheet is fixed so as not to be displaced in a region along the tubular light source in the frame region.

By fixing the optical sheet in a region along the tubular light source serving as a heat source, distortion of the optical sheet can be effectively suppressed and light leakage can be prevented.

According to a third aspect of the present invention, in the flat display device, the optical system sheet is hermetically fixed to a light-shielding frame body in a region along the tubular light source.

With this configuration, it is possible to reliably prevent light leakage due to distortion of the optical system sheet.

According to a fifth aspect of the present invention, in the flat display device, the optical system sheet is sandwiched between the display panel and the lamp reflector.

With this configuration, it is possible to reliably prevent distortion and light leakage of the optical system sheets without increasing the number of members and the number of assembling steps.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A flat display device according to an embodiment will be described.
This will be described with reference to a schematic longitudinal sectional perspective view of FIG. FIG. 1 shows an assembling structure of an edge portion on a side where a tubular light source is arranged, in a liquid crystal display device having an edge light type surface light source.

The flat display device 10 comprises a rectangular liquid crystal display panel 2 in which a plurality of pixels are arranged in an image display area 25;
It comprises a surface light source 3 therebelow (the back side, ie, the side opposite to the image display surface), and a frame structure for holding these.

The surface light source 3 includes a rectangular light guide plate 31 having substantially the same dimensions in the vertical and horizontal directions as the liquid crystal display panel 2, a tubular light source 32 arranged along one long side end surface of the light guide plate 31, It comprises a lamp reflector 33 having a U-shaped cross section which covers this tubular light source 32 in the vertical direction and from the outside of the panel.

The lamp reflector 33 includes a tubular light source 32.
Plays a role of a reflecting mirror that collects light emitted from the light source on the side end surface of the light guide plate 31. Lamp reflector 33
In addition, it functions as a frame body that holds and protects the tubular light source 32 and also serves as a protective cover that protects the tubular light source 32 from external impact. lamp·
The reflector 33 is formed by bending a metal sheet, such as stainless steel or aluminum, which is resistant to rust, into a substantially U-shape.

The lamp reflector 33 is fixed to the light guide plate 31 such that upper and lower ends 33a and 33b facing the inside of the panel sandwich the edge of the light guide plate 31 from above and below.

Although not shown, a plastic frame of the flat panel display 10 is arranged along the other three sides of the light guide plate 31. The plastic frame and the lamp reflector 33 constitute a frame structure of the flat panel display 10 together with the metal bezel cover 4.

The bezel cover 4 is made of a metal sheet.
As shown in the figure, the outer frame has a shape in which members having an inverted L-shaped cross section are combined in a frame shape. The bezel cover 4 covers the periphery of the upper surface of the display panel 2 and the four peripheral end surfaces, and is fixed to the plastic frame by screws or the like.

In the example shown in the drawing, between the upper surface of the surface light source 3, ie, the light emitting surface, and the lower surface of the display panel 2, the optical system sheets 11, 12, and 13 are superposed. The seat 1 is arranged. That is, the surface light source 3
The light source light emitted from almost the entire upper surface of the optical system passes through the three stacked optical system sheets 1 and enters the display panel 2.

Here, the optical system stacking sheet 1 is made of resin, and is formed by stacking two prism sheets 11 and 12 and a diffusion sheet 13. However, in some cases, a single laminated sheet composed of two or three layers may be used.

Each of the prism sheets 11 and 12 is formed by densely arranging a large number of fine ridges having a substantially regular triangular cross section so as to cover the upper surface. The two prism sheets 11 and 12 are
The parallel striped ridges are superimposed so as to be substantially orthogonal to each other. The prism sheets 11 and 12 have such a prism structure composed of a large number of minute projections to transmit light emitted upward from the light guide plate 31 in a direction directly above, that is, in a direction perpendicular to the display panel 2. It acts to focus. That is, it has an effect of improving luminance in the front direction of the flat display device or an effect of reducing power consumption of the surface light source.

On the other hand, the diffusion sheet 13 enhances the uniformity of the light source light emitted from the surface light source 3 in the emission surface,
As a result, variation in luminance is reduced.

As shown in the drawing, the optical system overlapping sheet 1 on the surface light source 3 extends to a position between the lamp reflector 33 and the display panel 2 on the side where the tubular light source 32 is disposed. That is, the optical overlap sheet 1 is sandwiched and fixed between the lamp reflector 33 and the display panel 2 in a region along the tubular light source 32 in the frame region.
The optical system overlapping sheet 1 is fixed only in this region, and is not fixed in the light source light emitting region and on the other three sides.

With this configuration, the heat generated by the tubular light source 32 is transmitted through the metal lamp reflector 33, and the optical system overlapping sheet 1 is locally heated near the lamp reflector 33. Also, the "undulation" and light leakage of the optical system overlapping sheet 1 are effectively prevented.

In addition, the number of man-hours and parts costs for manufacturing and assembling hardly increase.

Next, a modified example will be described with reference to FIG.

The flat panel display device 20 of the modified example has a configuration substantially similar to that of the above-described embodiment, and a band-shaped rubber packing 21 is previously attached to a position where the optical system overlapping sheet 1 is sandwiched on the lower surface of the display panel 2. It was done.

By disposing such a rubber packing 21, although the number of members is slightly increased, the fixing of the optical system overlapping sheet 1 and the prevention of light leakage can be performed more reliably. In addition, the rubber packing 21 allows the tolerance of design dimensions to be slightly increased during assembly.

In this modification, the band-shaped rubber packing 21 may be arranged not only in the region along the tubular light source 32 but also on all four sides of the display panel 2. Instead of the rubber packing 21, an elastic sealing member such as a soft foam of resin can be used. Further, even when an adhesive tape or the like is attached, the same effect can be obtained to some extent.

In the above embodiments and modifications, the tubular light source 32 has been described as being arranged along one long side of the light guide plate 31.
In the case of an L-shape or a U-shape arranged along 3 sides, the optical system overlapping sheet 1 can be fixed in such an area along the 2-3 sides. Also, in some cases,
The optical system overlapping sheet 1 can be fixed on all four sides surrounding the image display area.

[0046]

According to the present invention, distortion due to thermal expansion of optical sheets and uneven brightness caused by the distortion can be largely suppressed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional perspective view schematically showing a main part of a flat panel display device according to an embodiment.

FIG. 2 is a vertical cross-sectional perspective view schematically showing a main part of a flat display device according to a modified example.

FIG. 3 is a longitudinal sectional perspective view schematically showing a main part of a conventional flat display device.

FIG. 4 is a schematic diagram for explaining “undulation” of an optical system sheet in a conventional flat display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical system superposition sheet 11, 12 Prism sheet 13 Diffusion sheet (diffusion plate) 2 Liquid crystal panel 21 Strip rubber packing 3 Surface light source 31 Light guide plate 32 Tubular light source 33 Lamp / reflector 4 Bezel cover

Continuing from the front page (72) Inventor Yoshihiro Ogata 50, Kamiyube, Yobe-ku, Himeji-shi, Hyogo F-term in Himeji Plant, Toshiba Corporation (reference) 2H091 FA14Z FA21Z FA31Z FA34Z FA41Z FD01 FD06 FD11 FD12 LA03 LA04 LA18 5G435 AA02 AA12 BB12 BB15 EE03 EE27 FF03 FF06 FF08 GG00 GG03 GG24 HH18 LL04 LL08 LL17

Claims (6)

[Claims] 1. A light-transmitting display panel in which a plurality of pixels are arranged in an image display area; a surface light source disposed behind the display panel and emitting light source light to the display panel; In a flat display device including an optical system sheet disposed in a gap between the display panel and the surface light source in a region including a region, at least four of the frame regions surrounding the image display region from four regions. The flat panel display device, wherein the optical system sheet is sandwiched and fixed between the display panel and the surface light source so as not to be displaced in one side region. 2. The optical system sheet according to claim 1, wherein the surface light source comprises a substantially rectangular light guide plate, and a tubular light source disposed on at least one side of the substantially rectangular shape and close to a side end surface of the light guide plate. 2. The flat display device according to claim 1, wherein the frame is fixed so as not to be displaced in a region along the tubular light source in the frame region. 3. The flat display device according to claim 2, wherein the optical system sheet is hermetically fixed to a light-shielding frame body in a region along the tubular light source. 4. A flat display device according to claim 3, wherein said light-shielding frame is a lamp reflector. 5. A flat display device according to claim 3, wherein said optical system sheet is sandwiched between said display panel and said lamp reflector. 6. The flat display device according to claim 3, wherein an elastic sealing member is attached to a rear surface of the display panel corresponding to a region where the optical system sheet is fixed.